1. Related Field
The present patent application generally relates to serial storage architecture (or "SSA") storage subsystems and, more particularly, to a SSA storage subsystem having a SSA initiator and an intelligent backplane configured for the exchange of status and control information with the SSA initiator.
2. Description of Related Art
Presently, many storage subsystems are based upon small computer systems interface (or "SCSI") architecture. Recently, however, considerable attention has been directed towards the development of storage subsystems based upon SSA. Generally, SSA-based storage subsystems are capable of providing higher level of performance, fault tolerance, data availability and connectivity than is possible with similar SCSI-based storage subsystems. SSA-based storage subsystems also offer reduced interface costs. For example, SSA-based storage subsystems require no address switches and no discrete terminators.
SSA-based storage subsystems are arranged into a serial string of up to 128 devices, the ends of which are often connected to form a loop. Generally, such strings include an SSA initiator and any number of SSA targets, most commonly, storage devices such as drives, which execute commands received from the SSA initiator, mounted in drive bays. Each of the devices included in a string or loop has first and second full duplex ports.
Each device in an SSA-based storage system is sequentially addressed based upon its location within the string. If a device is added or removed from the string, a number of the other devices in the string will require re-addressing. While this ability to dynamically re-address devices has eliminated the need for user configurable jumpers, it is often difficult to spatially locate a particular device within a large storage subsystem based upon a machine assigned numerical address. Specifically, when in the storage subsystem, the string bypasses selected drives within a drive pod or is comprised of drives installed in plural drive pods. Thus, the task of locating and replacing a failed drive often proves unnecessarily complicated. Accordingly, there is often the need to communicate physical information regarding the drives of the string.
SSA storage subsystems have yet to satisfy this need. LEDs physically installed at each drive may convey information regarding drive activity and/or status but cannot be used for remote monitoring and control. Alternately, while it is possible to install a separate communication path for remote monitoring and control, such a solution would be quite burdensome.
It can be readily seen from the foregoing that it would be desirable to provide an SSA storage subsystem in which status and control information may be exchanged between the SSA initiator and the physical location where the storage devices included in the SSA storage subsystem are installed. It is, therefore, the object of this invention to provide such an SSA storage subsystem.